I am afraid I was too hasty with the IPv6 test pages, or maybe there is some caching going on, can't tell. Anyway, I fired up Internet Explorer and Google Chrome as well, both on Win7, to compare with Firefox on Win7 and Ubuntu. Turns out, the both test pages I mentioned give varying results on all rounds, and in multiple repeats, I could not ascertain significant differences between the four browser instances in the numbers the test reported. The only constant that remains is that the time Firefox on Win7 spends on loading and executing https://test-ipv6.com/ is much much longer than in the other instances. What makes this interesting is that (in the repeats) the other page http://ipv6-test.com seems to load approximately as fast also in Fireofx on Win7. The slowness only appears with https://test-ipv6.com/. Could this difference give any insight to what is going on, or is it just a matter of caching that masks the actual difference?

I know that it is not a very attractive solution but the users who cannot fix the issue with the delay should try it by creating a new profile under Firefox.

I did it (and it was a lot of work to configure it in the same way as the old one). But I can say that the delay is gone completely now - both when using Firefox inside and outside the sandbox. All runs smoothly again.

So perhaps you should give it a try. Anyway the creation of a new profile itself is quite simple. After the creation you can test immediately if the delay has gone. And only if you are satsified with the result you need to coninue with the cumbersome work of configuring the new profile.

Peter 123 wrote:So perhaps you should give it a try. Anyway the creation of a new profile itself is quite simple. After the creation you can test immediately if the delay has gone. And only if you are satsified with the result you need to coninue with the cumbersome work of configuring the new profile.

People trying this, and it is always a good idea to try a new additional testing profile, might want to confine their configuring to just copying over their bookmarks (places.sqlite) and passwords for a day or two.

I say that because based on other reports there's a fair chance the delay will appear on that profile within that time scale.

I was wrong about not having the problem on Ubuntu. Apparently I wasn't using FF as actively on Ubuntu, but the problem appeared there too. It clearly has something to do with opening connections to the various servers that the web pages load their content from.

By my untrained eye,it seems like FF takes lots of time with the handshakes, so much so that the serves often time out. But once the parts of a page are present, there is no problem any more. For example, I may have to refresh a page a few times to get all of its parts loaded, but once they are loaded, I can watch videos without interruption. Some pages behave differently. For example, I have to open my favourite route planner using some other browser altogether because the planner logic is based on loading different data sets to different parts of the page dynamically, and the problem in FF just plain makes it a nightmare.

Now, a new phenomenon has come up on top of it all. Every day at some point, FF freezes on both machines. I have to kill FF, restart it, kill it again, and restart it, etc. until the situation is over. On Ubuntu it seems to take more rounds than on Windows. The time of day is not always the same, but this happens on both machines within a minute or two. It's as if FF phones home or something, nearly at the same time on both machines.